lodash/test/before.spec.js

import lodashStable from 'lodash';
import { _ } from './utils';

describe('before', () => {
    function before(n, times) {
        let count = 0;
        lodashStable.times(
            times,
            _.before(n, () => {
                count++;
            }),
        );
        return count;
    }

    it('should create a function that invokes `func` after `n` calls', () => {
        assert.strictEqual(
            before(5, 4),
            4,
            'before(n) should invoke `func` before being called `n` times',
        );
        assert.strictEqual(
            before(5, 6),
            4,
            'before(n) should not invoke `func` after being called `n - 1` times',
        );
        expect(before(0, 0), 0).toBe('before(0) should not invoke `func` immediately');
        expect(before(0, 1), 0).toBe('before(0) should not invoke `func` when called');
    });

    it('should coerce `n` values of `NaN` to `0`', () => {
        expect(before(NaN, 1)).toBe(0);
    });

    it('should use `this` binding of function', () => {
        const before = _.before(2, function () {
            return ++this.count;
        });
        const object = { before: before, count: 0 };

        object.before();
        expect(object.before()).toBe(1);
        expect(object.count).toBe(1);
    });
});